The present invention relates to kerosene lanterns; and more particularly, it relates to apparatus for preheating the generator tube of a kerosene lantern with the capability of using kerosene as the preheating fuel.
Kerosene lanterns of the type with which the present invention is concerned have been known and commercial available for many years. Typically, kerosene is stored in a closed reservoir or fount which is pressurized with a hand pump. Liquid fuel is communicated through a valve to a generator tube in which the liquid fuel is heated to vaporization. The vaporized fuel is then fed to a mixing chamber of a Bunsen tube where the fuel vapor is mixed with air. The air/fuel mixture is fed through the Bunsen tube to a burner head for heating a mantle to produce light.
Kerosene lanterns are considered to be a convenient and safe source of light, and they operate reliably and well once equilibrium temperatures are attained for vaporizing the fuel in the generator tube and for burning adjacent the mantle. One of the main advantages of using kerosene, as distinguished from gasoline, for example, as a lantern fuel is that it has a relatively high vaporization temperature and is therefore safer in use. This characteristic, however, makes it difficult to vaporize the fuel in the generator tube during starting. This difficulty has been a major problem with kerosene lanterns since their early introduction. During normal operation the heat from the burner head or mantle is sufficient to cause a self-sustaining vaporization of the fuel in the generator tube.
A number of solutions has been suggested to overcome the starting problem. One approach (and perhaps the most common technique currently used commercially), is to employ a separate, more easily combustible fuel, such as alcohol, to be burned adjacent the generator tube, until it is heated sufficiently to sustain continuous operation. One disadvantage here is that it is cumbersome and dangerous to require a separate fuel. Further, there are objections in certain localities to the use of alcohol in this connection. Kerosene cannot be used as the auxiliary fuel in these structures for two reasons. First, when kerosene is burned in an open cup, the resulting flame is too small to preheat the generator sufficiently to cause self-sustaining operation. Secondly, such a flame is sooty; and the soot deposits on the interior of the glass surrounding the mantle, thereby diminishing the usable light from the lantern.
To overcome the requirement of an auxiliary fuel as described above, another commercial embodiment employs a separate blow torch which draws fuel from the main reservoir and directs the resulting flame onto the generator tube until it is sufficiently heated. The principal disadvantage to this structure is that the cost of the blow torch apparatus is substantial in relation to the overall cost of a kerosene lantern which is fairly modest. It will be appreciated that one of the principal uses of kerosene lanterns is to provide light in areas of the world where electrification has not taken place, and so the cost of a lantern is a significant factor in its commercial acceptability.
In co-owned U.S. Pat. No. 2,263,659, the pressurized air and fuel vapor mixture above the fuel in the fount is drawn off and discharged as an atomized mixture into a burner tube which is directed toward the generator tube to heat the generator. This system requires special atomizer apparatus, and it also requires that a person tend the lantern to turn off the preheat device once the generator tube has been sufficiently heated to vaporize the fuel within it.
In accordance with the present invention, an economical, yet convenient and reliable preheat apparatus is provided for a kerosene lantern and which is capable of using kerosene for the preheating fuel. A reservoir cup is provided adjacent the generator tube, and a measured amount of fuel, drawn from the fount, is deposited in the reservoir. A wick is located in the reservoir and is surrounded by a foraminous housing which extends around and above the wick. The wick is carefully tailored as to size and surface area, so as to burn a given quantity of fuel in a fixed amount of time. If the wick fails to burn a sufficient amount of fuel in the proper time, the generator will not be heated enough. If the wick burns too much fuel in this time, the foraminous housing can no longer entrain enough air. This results in a wide sooty flame which burns around the outside of the housing. A wide sooty flame will blacken the interior of the globe.
The foraminous housing is sized and shaped to operate in cooperation with the wick. The holes provide for a controlled entrainment of air with the vaporized fuel during burning. The shape and an upper aperture of the housing serve to direct the flame into a tall, narrow shape which envelops the generator. A small amount of soot is created by this tall narrow flame, but the soot exists above the top of the glass, and it is deposited on the underside of the lantern top. Therefore, the glass remains clean. Kerosene may thus be used as a preheating fuel.
Preferably, the apparatus includes some type of measuring dispenser such as an eyedropper or a rubber bulb syringe to deposit a precise, measured amount of fuel into the preheat reservoir. In the preferred embodiment, the measuring device is stored in the lantern collar. By using a measured amount of fuel, it is insured that the preheat apparatus burns long enough to heat the generator under the coldest conditions, and that the preheat fuel will burn out when the heat from the mantle is capable of vaporizing fuel in the generator.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.